Synthesis and characterization of layered perovskite-type oxides LnSr2MnFeO7 (Ln = La, Nd, Gd, and Dy)

Layered perovskite-type oxides LnSr2MnFeO7, with Ln = La, Nd, Gd, and Dy, have been synthesized by conventional solid-state reaction method. Rietveld refinement shows that all the phases were found to crystallize with tetragonal unit cell in the space group I4/mmm. The unit cell parameters a and c decrease monotonically with decreasing effective ionic radius of the lanthanide ion. The phases show insulating behavior with no anomalous features in the entire temperature range of 150–350 K and the electrical conduction occurs by Mott’s variable range hopping mechanism. The magnetic studies suggest that the phases are antiferromagnetic and the Weiss constant (θ) increases with decreasing ionic radius of lanthanide ion.